Engineering Drawing
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Traditional Drawing Tools
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DRAWING TOOLS
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DRAWING TOOLS
1. T-Square
2. Triangles
HB for thick line 2H for thin line
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DRAWING TOOLS
3. Adhesive Tape
4. Pencils
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DRAWING TOOLS
5. Sandpaper
6. Compass
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DRAWING TOOLS
7. Pencil Eraser
8. Erasing Shield
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DRAWING TOOLS
9. Circle Template
10. Tissue paper
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DRAWING TOOLS
11. Sharpener
12. Clean paper
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Freehand Sketching
Straight Line
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2. Spot the beginning and end points.
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1. Hold the pencil naturally.
3. Swing the pencil back and forth between the points, barely
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touching the paper until the direction is clearly established.
4. Draw the line firmly with a free and easy wrist-and-arm
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motion
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Horizontal line
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Vertical line
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Nearly vertical inclined line
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Nearly horizontal inclined line
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Method 1 : Starting with a square
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Small Circle
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1. Lightly sketching the square and marking the mid-points. 2. Draw light diagonals and mark the estimated radius.
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3. Draw the circle through the eight points. Step 2
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Step 1
Step 3
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Method 2 : Starting with center line
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Small Circle
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1. Lightly draw a center line.
2. Add light radial lines and mark the estimated radius.
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3. Sketch the full circle.
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Step 2
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Step 1
Step 3
Arc
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Method 1 : Starting with a square
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Method 2 : Starting with a center line
Horizontal
Curved
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Slanted
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Straight
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Basic Strokes
Examples : Application of basic stroke “A” letter 1
2
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“I” letter
“B” letter 1
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3 3
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Upper-case Strokes letters & Sequence Numerals Suggested
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Straight line letters
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Curved line letters & Numerals
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Curved line letters
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Lower-case letters Suggested Strokes Sequence
letter.
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The text’ s body height is about 2/3 the height of a capital
Example : Good and Poor Lettering
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GOOD
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Not uniform in style.
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Not uniform in height.
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Not uniformly vertical or inclined. Not uniform in thickness of stroke.
Area between letters not uniform. Area between words not uniform.
Sentence Composition
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Leave the space between words equal to the space requires for writing a letter “O”.
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Example
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ALLODIMENSIONSOAREOIN MILLIMETERSOUNLESS OTHERWISEOSPECIFIED.
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GRAPHICS LANGUAGE
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1. Try to write a description of this object.
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Effectiveness of Graphics Language
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2. Test your written description by having someone attempt to make a sketch from your description.
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You can easily understand that ‌
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The word languages are inadequate for describing the size, shape and features completely as well as concisely.
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Composition of Graphic Language
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edges and contours of objects.
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Graphic language use lines to represent the surfaces,
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The language is known as “drawing” or “drafting” .
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A drawing can be done using freehand, instruments or computer methods.
Freehand drawing
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The lines are sketched without using instruments other than pencils and erasers.
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Example
Instrument drawing
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Instruments are used to draw straight lines, circles, and curves concisely and accurately. Thus, the drawings are usually made to scale.
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Example
Computer drawing
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such as AutoCAD, solid works etc.
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The drawings are usually made by commercial software
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Example
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Architectural Graphics
Elements
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Drawing comprises of graphics language
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Word language
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Describe a shape (mainly).
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Graphics language
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and word language.
Describe size, location and specification of the object.
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Basic Knowledge for Drafting
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Word language
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Geometric construction
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Projection method
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Line types
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Graphics language
Lettering
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PROJECTION METHOD
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PROJECTION METHOD
Perspective
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Parallel Orthographic
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Oblique
Axonometric
Multiview
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PROJECTION THEORY
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The projection theory is used to graphically represent
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3-D objects on 2-D media (paper, computer screen).
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The projection theory is based on two variables: 1) Line of sight
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2) Plane of projection (image plane or picture plane)
Line of sight
is an imaginary ray of light between an
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observer’s eye and an object.
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There are 2 types of LOS : parallel and converge
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Line of sight
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Parallel projection
Perspective projection
Line of sight
Plane of projection is an imaginary flat plane which
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the image is created.
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The image is produced by connecting the points where
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the LOS pierce the projection plane.
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Plane of projection
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Parallel projection
Perspective projection Plane of projection
1) It is difficult to create. 2) It does not reveal exact
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shape and size.
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Disadvantage of Perspective Projection
Width is distorted
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Orthographic Projection
MEANING
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Orthographic projection is a parallel projection technique
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in which the parallel lines of sight are perpendicular to the
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projection plane
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Object views from top
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3 4 Projection plane
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ORTHOGRAPHIC VIEW
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Orthographic view depends on relative position of the object
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to the line of sight.
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More than one view is needed to represent the object.
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Two dimensions of an object is shown.
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Multiview drawing
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Three dimensions of an object is shown. Axonometric drawing
Rotate
Tilt
ORTHOGRAPHIC VIEW
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NOTES
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Orthographic projection technique can produce either
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1. Multiview drawing that each view show an object in two dimensions.
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2. Axonometric drawing that show all three dimensions of an object in one view.
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Both drawing types are used in technical drawing for
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communication.
Axonometric (Isometric) Drawing Easy to understand
Disadvantage
Shape and angle distortion
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Distortions of shape and size in isometric drawing
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Circular hole becomes ellipse.
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Example
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Advantage
Right angle becomes obtuse angle.
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Types of Axonometrics
Multiview Drawing
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It represents accurate shape and size.
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Advantage
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Multiviews drawing (2-view drawing)
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Example
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Disadvantage Require practice in writing and reading.
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The Glass Box Approach
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Orthographic Projection
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Opening the Box
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Final Views
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Six Orthographic Views
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Laying Out All Six Views
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Three Primary Views
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Construction of Views
Third-angle Projection
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First and Third Angle Projections
First-angle Projection
• First Angle – International • Third Angle – U.S.
Basic Line Types
Continuous thick line
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Dash thick line
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Continuous thin line
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Chain thin line
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Name according to application
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Appearance
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Types of Lines
Visible line Dimension line Extension line Leader line Hidden line Center line
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Meaning of Lines
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current view
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Visible lines represent features that can be seen in the Hidden lines represent features that can not be seen in
represents symmetry, path of motion, centers
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Center line
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the current view
of circles, axis of axisymmetrical parts
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Dimension and Extension lines indicate the sizes and
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location of features on a drawing
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Example : Line conventions in engineering drawing
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Good practice
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Exercise
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• Complete three orthographic views of the object shown on the next slide. • Include visible, hidden, and center lines where appropriate. • You will be given 7 minutes.
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Object for exercise
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Solution
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Drawing Standard
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Introduction
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drawings are represented.
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Standards are set of rules that govern how technical
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Drawing standards are used so that drawings convey
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the same meaning to everyone who reads them.
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Standard Code
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Full name
Code
USA
ANSI
American National Standard Institute
Japan
JIS
Japanese Industrial Standard
UK
BS
British Standard
Australia
AS
Australian Standard
Germany
DIN
Deutsches Institut fĂźr Normung
ISO
International Standards Organization
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Country
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Partial List of Drawing Standards Contents
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Code number
Sizes and Format of Drawings
JIS Z 8312
Line Conventions
JIS Z 8313
Lettering
JIS Z 8314
Scales
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JIS Z 8311
JIS Z 8316
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JIS Z 8317
Projection methods
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JIS Z 8315
Presentation of Views and Sections
Dimensioning
Drawing Sheet
Standard sheet size (JIS)
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210 x 297 297 x 420 420 x 594 594 x 841 841 x 1189
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A4 A3 A2 A1 A0
A2
(Dimensions in millimeters)
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A4
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Trimmed paper of a size A0 ~ A4.
A0
Orientation of drawing sheet 1. Type X (A0~A4)
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2. Type Y (A4 only)
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Drawing space
Drawing space
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Title block
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Sheet size A4 A3 A2 A1 A0
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Border lines
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c (min) d (min) 10 25 10 25 10 25 20 25 20 25
Title block
Length, size
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Drawing Scales
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Scale is the ratio of the linear dimension of an element
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of an object shown in the drawing to the real linear
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Size in drawing
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dimension of the same element of the object.
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Actual size
Drawing Scales
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Designation of a scale consists of the word “SCALE”
SCALE 1:1
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followed by the indication of its ratio, as follow for full size
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SCALE X:1 for enlargement scales
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SCALE 1:X for reduction scales